Peaceful aliens will be met with fear and greed, as humans try to kidnap, interrogate, dissect them, etc. They'll usually think the aliens want to attack. Said aliens may gain one or two human friends (the main characters) but most of the human race is shown to be primitive fools. Humans Are the Real Monsters. It is a Sub-Trope of Misunderstood Loner with a Heart of Gold with its own flavor. Incidentally, this trope is a staple element of at least some parts of ufology, among those who believe in it.

Evil aliens will either outright attack, or manipulate themselves into positions of power over humanity, made more easy by the hordes of naive humans who just want to be friends, which shows most of the human race to be primitive fools. Only a few will know the truth, and try to convince everyone else that "it's a cookbook!" This is a Sub-Trope of Subverted Suspicion Aesop with its own flavor.

It's a Schrödinger's Gun; mankind is either an aggressive oppressor or clueless victim, and never in the beneficial combination. The trope name comes from the signature line of "Captain Kirk" in the song "Star Trekkin'" by The Firm.

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In Soukou no Strain, the peaceful Emilies are dissected for their psychic power, leading them to attack; we learn from the two Emilies in the series that it doesn't go well.

The Arume in Blue Drop change policy regarding rule of the humans so frequently that they've gone through pretty much every point on this scale at least once in the metaseries.

The Riofaldians in Cannon God Exaxxion make a big show of being friendly with the humans when they first show up. Of course it turns out this was just a ploy to make preparations for their Vichy Earth ambitions go more smoothly.

In Archie'sSonic the Hedgehog, humans dissecting the occupant of a downed Xorda spacecraft caused the entire race to launch genetic bombs at the Earth, thus killing off most humans and causing evolutionary mutation that led to our furry friends, the Mobians, becoming a dominant species along with the human-like Overlanders.

Pretty much the same thing happens, without the Karmic Death, in an issue of Planetary. Except that the killer in question was a government operative there to salvage technology who showed no signs of considering the kid a threat, and simply thought that his boss wouldn't want to have to deal with it. Ironically, just after he did the order came in to bring the child in for study.

Inverted (for a Version 2) in both the last arc of Marvel's X-Man and the Maximum Security Crisis Crossover, in which a clueless farming couple attempt to rescue an "alien baby" who turns out to be a biosphere-devouring menace.

ROM Spaceknight: Initially played straight as the villain shapeshifting Dire Wraiths are able to easily convince most of the people of Earth that Rom is a murderous marauder. However, this trope is later averted when the Dire Wraiths get more brazen and the Earth authorities realize that Rom's story about the menace of his enemies is real and throw their complete support behind the space knight, including making him field leader for hunting expeditions with SHIELD agents.

The very first issue of Paperinik New Adventures starts with the Evrons overwhelming the last Xerbian stronghold on their homeworld. Two issues later we find out from Xadhoom it was this trope in action: the Evrons, knowing that their army was superior to the Xerbian glorified police force but their ship wouldn't survive against the planetary defenses, sent ambassadors to sign a 'commercial agreement', and as soon as Xerba's planetary defenses were temporarily deactivated as sign of peace the Evron 'freighters' disgorged hordes of soldiers, overwhelming the Xerbians in a matter of days, with Xadhoom returning on the planet just in time to see the end of the last stronghold.

In Spores we discover the Evrons are trying the same thing on Earth, trying to lull the United States and a Ruritania in a sense of peace, with the implied reason being that Earth is the exact opposite of Xerba: the Evrons can land, but there's no guarantee their soldiers would win (in fact they got their asses handed to them by human troops four times on-screen, one of them showing that Evrons with air support will win, albeith with heavy losses, but as soon as the battle moved into the corridors of the attacked base the US Army needed just a couple minutes of pause to muster a counterattack that won the day with the power of More Dakka). Also, they know that Earth weapons can shoot down their landing ships (a dozen assault helicopters at short range of one of their heavily armed assault ships were treated as an instant victory for the helicopters, and a blimp filled with TNT exploding near one of their 'Invasion Hives' in the upper atmosphere was enough to shoot it down), and while they know they can destroy our missiles they have no idea of how many nukes we have, and just one of them going off in a cluster of ships would annihilate them.

Displayed quite nicely in Independence Day, in which a horde of Genre Blind people has assembled atop a skyscraper waving "hello and welcome to Earth" placards as the alien spaceship positions itself directly over them... and then fires its massive "frission" cannon, destroying the building and most of the city. Earlier, the government sent a helicopter rigged with a grid of flashing lights to try and communicate: the aliens promptly blew it out of the sky.

Subsequently parodied in Mars Attacks!! The Martian ambassador comes up to a podium and speaks into a translation device, translating his words as "We come in peace". Then they whip out the rayguns and incinerate everyone in sight- at first, seemingly in response to a "cultural misunderstanding" where "dove means war", but it quickly turns out they are just doing it For the Evulz. Later, during the full-scale genocide, one of the Martians is carrying the translation device, which now broadcasts "Do not run! We are your friends!" over and over.

Starman (the movie, and then the TV series based on it) was about a friendly alien who was hounded by the government. He first came to Earth in response to our friendly greetings carried aboard one of the Voyager probes... and was promptly shot down.

Gamera: Guardian of the Universe (1995) featured a variation. Although not aliens, the army incorrectly decides that Gamera, a benevolent Anti-HeroKaiju created specifically to protect the Earth, is the real threat, while the evil, destructive, man-eating Gyaos are a nuisance by comparison.

The third movie, Revenge of Iris, has an interesting variation: while Gamera is shown in his darkest portrayal yet (a fight at the start of the movie with a Gyaos in downtown Tokyo causes at least 12000 casualties, at least half from Gamera's Breath Weapon, and he's proven to be an incarnation of Gaia's Vengeance), it's shown pretty conclusively that he's by far the best alternative despite this, as other monsters are far more hostile to humanity and likely won't stop until they or humanity are wiped out and besides, the last scene of the movie depicts a massive Gyaos outbreak (as in a flock of thousands of the buggers, ranging in size from a VW Beetle to stadium-sized) and a spent, wounded Gamera soldiering on and preparing to go and face them for the sake of humans

Invasion of the Astro Monster has evil aliens claiming they need help to get rid of a giant monster known to the aliens as "Monster Zero" (it's King Ghidorah) in exchange for your average intergalactic secrets. The earthlings are only too happy to send Godzilla and Rodan to stop Monster Zero. And, evil aliens being evil aliens, it turns out that they were controlling Monster Zero the whole time and they then use Mind Control on Godzilla and Rodan as well and unleash all three monsters unto Japan.

While technically not aliens, the Futarians from the 1990s film Godzilla VS King Ghidorah qualify here. They act as if they're helping Japan by removing Godzilla from history, but, in reality They just need to get rid of Godzilla so they can replace him with their own monster Ghidorah.

Played as allegory in District 9, where despite evidently superior firepower the "prawns" take on the role of African refugees and generally accept their poor treatment.

The vast majority were basically "worker bees" who didn't really do anything unless a "Commander" (like the one the main character teamed up with) gave them direction.

Played with in Moontrap, where the scientist who wants to talk to the alien cyborg changes his mind after it shoots him and tells the security detail to "Get the son of a bitch!". Too bad he forgot that he is down-range.

The Iron Giant: Everyone initially assumes the Giant is hostile despite lack of evidence that it's hurt anyone; Kent Mansley in particular refuses to be convinced to the end. In a twist, he'd probably be right if it weren't for the damage to the Giant's programming; all the weaponry it carries suggests its original purpose was less than friendly.

Given the fact that they're tied as an automatic reaction for self-defense and are only used when it's perceived to be in danger, it's also possible that its purpose was simply to scout or explore, and the weaponry was there to defend it against absolutely anything that might impede its mission.

In a cut scene, the Giant has a dream that strongly implies he was part of a robotic invasion force.

The 2012 sci-fi parody film Iron Sky uses this as one of its tag lines. The film is about SpaceNazis invading the Earth.

A somewhat clever twist occurs in one Maximum Boy novel where alien cows decide to visit earth: The cows state that they come in peace, but state that how they leave depends on what they find. Sure enough.....

Skewered in George Alec Effinger's hilarious 1984 short story, The Aliens Who Knew, I Mean, Everything: the aliens who visit, called the Nuhp, really do come in peace, and really are willing and able to help solve at least some of Earth's problems. Unfortunately, they're also such an annoying bunch of know-it-alls, that their presence gradually becomes more curse than blessing. Eventually, humanity leaves Earth in droves to get away from the Nuhp... and the resultant population reduction solves the rest of Earth's problems by default. Turns out this happens on every planet the Nuhp visit, and space is filled with species that left their homeworlds to get away from them.

Stanislaw Lem's novel Fiasco features a human starship on a mission to "peacefully make contact" with the inhabitants of the planet Quinta. This proves difficult when they discover that Quintan civilization is consumed with an internal conflict that has led the antagonistic factions to garrison their entire solar system with powerful automated war machines. Despite the humans having a substantial technological edge over the Quintans, a series of misunderstandings, miscommunications, and double-crosses ensues, accompanied by escalating shows of force that culminate in the humans blowing up the entire planet.

Happens with the Pitar in Alan Dean Foster's books set in the Humanx Commonwealth. They were so human in their appearance and character, so charming and affable, that Humanity went head over heels about them. Any suspicions were either ignored in this wave of enthusiasm, or quietly swept under the rug. Until the news got out (complete with gory footage) about a peaceful and unarmed colony utterly obliterated by the Pitar invasion fleet. Humans were not amused.

The first encounter between humans and the the Kzinti (in the first Man-Kzin Wars collection) was the peaceful human explorers on an unarmed ship being slowly roasted by an Kzinti warship to test human tolerances... and then the captain basically says "screw it" and cuts the attacking ship in half with concentrated engine exhaust and loots the weapons off the wreck. The tag for the series was that humans had decided to study war no more because we're too good at it.

Used as a cover story by the Grigari in Deep Space Nine's Millennium trilogy. The Grigari "mistook Earth's intense sensor scans" for an attack, then "fired a warning shot" that they "didn't realize would overwhelm the planetary defenses". Result: Earthshattering Kaboom.

According to Diane Duane's Star Trek novels, the Vulcans were once invaded by Orion Pirates who "came in peace." Since then, the Romulans (which left Vulcan after that ... long story) have been a bit wary of peaceful intentions, as Starfleet later found out.

To explain what happened: first the USS Carrizal arrived, and, after verifying that the Romulans were space-capable, did everything they could to be seen, show they came in peace, broadcasted their intentions and the basic first contact data, and when the Romulans didn't answer they left; three years later the USS Balboa arrived to make another attempt, but survived only long enough to see that the Romulans had built a powerful net of war satellites and launch a desperate distress call before being disintegrated by the guns of fifty small warships out of the seven thousands they had built; when the USS Stone Mountain answered the distress call, the Romulans captured it, killed the whole crew and started taking it apart, improving their technology and getting warp capability in case the Federation didn't understand their message of 'leave us alone or die'.

The same is pretty much the case in Fred Saberhagen's Berserker stories; the Carmpan, an inherently peaceful race unable to directly fight the titular killing machines, gives humanity just enough help to become expert Berserker-killers.

A subversion in another John Ringo work, Live Free or Die: The initial contact is peaceful, by a race that's only interested in trade with Earth. Contact with the Horvath is... not, and for rather less pleasant purposes than trade.

Dreamcatcher by Stephen King involves an invasion by an alien species of telepathic mold (It Makes Sense in Context). The mold sends out telepathic messages which includes the classic "We come in peace", but the big lie is "We are not infectious".

Played with in Halo: Contact Harvest. First contact between humanity and the Covenant happened between a group of Marines and Jiralhanae (a.k.a.Brutes). The Jiralhanae are making unreasonable demands during the negotiations, but that's not what starts the Human-Covenant War. Instead, it was a trigger-happy Grunt.

Played with in Harry Turtledove's short story "The Road Not Taken". When aliens land, humans send out peaceful processions to greet them, which are quickly massacred by the landing party. However, the humans also very reasonably have military units nearby, just in case. The twist is that, other than their space travel capabilities, the aliens are ridiculously out of their league, technologically (attacking with flintlock rifles and powder cannons). The invasion is routed almost immediately.

New Doctor Who plays this one straight: The Master goes to Earth, creates a human identity for himself, and gets elected as Prime Minister. Then he calls in the Toclafane, who come to Earth under the pretense of sharing their technology in exchange for Earth's friendship. Moments after first contact, however, the Master and the Toclafane set their true agenda into motion: take over the world so they can build warships and conquer the rest of the universe. Earth humans are literally (in the Latin sense of the word) decimated.

The Silurians have elements of Category 2, with the Doctor castigating UNIT for being trigger-happy. But the Silurians themselves are conflicted, with some of them wanting peace and others releasing a plague on London.

The Big Finish audio drama "Blood of the Daleks" features a beleaguered human colony being contacted by "benevolent aliens". The clue's in the title. (And at the end they make the same mistake with the Cybermen.)

Army of Ghosts demonstrates a variation whereby the visitors are not aliens but Killer Robots called Cybermen from a Parallel Universe, being deliberately brought to ours by the Torchwood institute. (In the first act of the episode, the Cybermen take on a "ghostly" appearance and do not speak). During the period where the visitors are assumed to be friendly, humans call them "ghosts", and many even think they really are the silent spirits of their deceased loved ones. The Doctor says "No one's running, screaming, freaking out", to which Jackie responds "Why should we?" Correct answer, for the Genre Savvy: Because you aren't, which means they're probably dangerous.

There was a great line at the end of that episode.

Yvonne: They're invading the whole planet.The Doctor: It's not an invasion, it's too late for that. It's a victory.

V: The Series (itself a followup to two miniseries) was about a hostile, sneaky, Nazi-like alien race using humanity's credulity against them.

Originally conceived as a show about the presidency of a Father Coughlin like American fascist, but the network demanded Nazis IN SPACE!

The 2009 reboot makes it the alien leader's catchphrase: "We are of peace, always." (Major spoiler: No, they aren't.)

Stargate SG-1 is often an exception. The aliens they make first contact with are rarely evil, and it's even more rare for the protagonists to try to do them any harm. They're just incredibly unlucky.

Only if you count all the non-Earthborn humans as aliens like the SGC does. The few real aliens fit the trope much better.

Not sure which aliens you mean... the Goa'uld and Wraith, obviously, but the Asgard are clearly helpful (though some of them are occasionally pompous), the Tok'ra are generally helpful all around (with occasional exceptions), the Nox are isolationist pacifists, the Unas are primitive, but eventually helpful, and the Serrakin are at first set up to be evil, but it turns out to be some humans that the Serrakin captain was with that are the bad guys. If you count the Jaffa as aliens (which, due to genetic modification, I'd say they are), their development from cannon fodder minions to a free people is at the heart of the show. Can't think of any more aliens off the top of my head, except the Furlings, but we've never seen them outside of the joke in Episode 200.

The Ori in the last several seasons would fit rather well. They attempt to spread the religion of Origin throughout the Milky Way, having their priors say that it's enlightenment, the Ori are gods, and that they'd teach ascenscion. Really, they just want the power your worship will give them, and if you don't convert, they'll kill you and maybe your entire planet.

There is a good example of the manipulative version in the Aschen, who, after giving mankind a crapton of Applied Phlebotinum, including a serum which doubles their lifespan, are discovered to be sterilizing the human population, so that they will eventually die out, and the Aschen can take over the planet. They are of course found out, but too late, requiring a Time TravelRetcon. SG-1 has a lot of those.

Around five. That might be plenty for a normal show, but this thing went on for ten seasons.

Ba'al in Stargate Continuum does a textbook example of this, even phoning the President to tell him that he comes in peace, knowing that a direct attack would make things much harder. It would have worked if there hadn't been a time traveling La Résistance waiting for his arrival.

Subverted quite nicely in Earth: Final Conflict. When the show starts the aliens do have a great deal of influence, but many humans are still untrusting. More significantly, while the aliens do have a hidden agenda, it's not so much EVIL as a gambit driven by a desire to survive.

Not even ONE gambit, but several, which generally end up anything from failing to being near-cataclysms (having so many of them, often working at cross-purposes, getting in each other's way, or at the least diverting important ressources from each other turns out not being a great idea. Go figure).

Subverted by 3rd Rock from the Sun. The friendly alien protagonists live in constant fear of being experimented on by "primitive" Earth scientists and use this as the justification for their Masquerade. The subversion comes in how paranoid they are about this happening even though none of the human characters even suspect they're aliens. Well, except for that one psycho played by Kathy Bates, but it turns out she had a habit of killing innocent people she incorrectly suspected of being aliens.

The main characters of Roswell are just three (or, for a while, four) teenagers who only want to live in peace until they figure out a way to get home, but they live in constant - and justifiable, given certain events of the first season - fear of the government and other alien hunters.

Captain Archer of the NX-01 Enterprise sets forth on a mission of exploration and derides the need for powerful weapons, but three years of Close Encounters of the Worst Kind and the deaths of 27 crewmen in the Xindi conflict cause him to recommend that the NX-02 be better armed and have a squad of MACO's as well.

The prologue to "In a Mirror, Darkly" takes the beautifulFirst Contact scene where humanity meets the Vulcans, flips it inside-out and drops it squarely into Type 1 of this trope—Zefram Cochrane blasts the Vulcans in the face with a shotgun and hijacks their ship. Pretty awesome, in a sadistic sort of way.

On Babylon 5, such an incident kicked off the pre-series Earth-Minbari War. During the first contact between Earth and Minbari starships, the Minbari approach with gunports open, a cultural gesture of respect. The Earth captain overreacts -- the Minbari accidentally jam the Humans' jump drives with their scanners -- and assumes hostile intent. Hilarity Ensues.

In the Twilight Zone episode "To Serve Man" (based on the Damon Knight story of the same name), outwardly-benevolent aliens visit us and grant us all of their technological wonders, including indestructible force-domes that protect each nation from nuclear attack by any other nation. We accidentally get hold of their handbook, titled "To Serve Man". Guess which kind of "Serve" they had in mind?

The first version is explored in the lesser known episode "The Gift". An alien makes contact with a superstitious Mexican town and is killed out of fear. The villagers find he had a paper as a gift saying "Greetings to the people of Earth. We come in peace. We bring you this gift. The following formula is a vaccine against all forms of cancer...." the rest of the page burned away.

Chris Elliott did a sketch on some show parodying the "all aliens are friendly" by hugging and promoting one trying to attack him.

This is the Backstory to Necessary Evil. A friendly alien race comes to ally with Earth's super heroes in their endless battle against another, warrior alien race. After a long battle with the enemy, the good aliens drive off the evil ones and all of the heroes gather up to throw a celebration in their honor. It turns out to be an elaborate trap. The good aliens and the evil aliens are both on the same side, and fabricated the war in order to gather all of the super heroes in the same place at the same time. Following the extermination of the good supers, the aliens enslave humanity and rule with an iron fist leaving only the super-villains to fight for humanity.

First contact in Mass Effect for humans came in the form of the turians discovering human explorers activating inactive mass relays whenever they found them. This is a big no-no by turian reckoning, and their response was to shoot first and not bother asking questions until the other Citadel species got involved.

The humans had also inhabited empty planets on turian territory without knowing it. What the turians saw was an unknown race of aggressive expansionists who wantonly ignored all the Citadel Conventions that they were sworn to protect. The humans in turn saw a bunch of aliens attacking their new colonies for no reason. It took the diplomacy of the asari to solve that mess. While humanity is a force to be reckoned with by the time the game begins, the asari basically kept the turians from getting serious about the war and turning humanity into a historical footnote. Indeed, the Council ordered the turians to pay reparations to the humans. (They then proceeded to keep the Systems Alliance carefully in check.)

"Footnote" is a bit light. While there's no doubt the Council would have eventually won, it also mentions that in the process the fighting would have devastated a large part of the galaxy, due in no small part to the fact that humans were not abiding by Council military limitation laws at the time. Humans in this universe are scarily strong, and getting stronger.

There were only two real battles in the "relay 314 incident." In the first the Turians took over a small, basically undefended outpost full of mostly civilian humans who didn't know aliens existed, let alone needed to be defended against. In the second, the combined human fleet came and removed the relatively small turian force that was occupying the colony and thinking that they had nothing to worry about but a small, primitive species of barely spacefaring apes. If it had expanded into a real war, there's no telling who would have come out on top, and there would definitely have been billions of casualties on both sides.

The Esmers in Little Big Adventure 2: Twinsen's Odyssey. Their catchphrase: "Greeting Twinsunian! We are your friends. We come in peace. Have trust in your friendship!" is so suspiciously harmless that it is really no surprise when they turn out to be not so nice after all. The fact that they fire guns at you from behind newspapers and even dress up as cacti and trash cans to shoot at you further exemplifies this.

The Backstory to X-COM: UFO Defense has humanity repeatedly trying to contact the alien invaders and being ignored. Although the aliens weren't really bad guys at that point (there were UFO sightings, but relatively few abductions), there wasn't much of a problem other than the diplomatic equivalent of getting the cold shoulder. Then the aliens attacked a city. Let's round up a posse and kick their alien asses!

In addition, in both UFO Defense and Terror from the Deep, the aliens will try to convince territorial governments of their good intentions. If they succeed, the government ceases funding X-COM and the aliens actually don't attack them any more. If all governments sign non-aggression pacts with the aliens, then the aliens summarily destroy humanity. Whoops!

The trope title is a criminal offence in Startopia, which will occasionally show up on criminal peeps that enter your station.

The Slylandro probes in Star Control II appear peaceful, but change their minds when you terminate the conversation. Turns out the Slylandro just suck at programming; they dialed up the probes' self-replication ability too high, resulting in them dissecting the targeted ship for materials to make more probes.

The various Transformers series have had both, at times: The fiendish Decepticons worming their way into humanity's places of power, and the heroic Autobots being hounded as invaders (often after the Decepticons reveal themselves).

Parodied in the Futurama episode "Roswell That Ends Well", when Harry S Truman greets Zoidberg with "If you come in peace, surrender or be destroyed. If you're here to make war, we surrender."

In the Superfriends episode, "Volcano," an alien ship crashes lands into an active volcano. Superman and Samurai come to render assistance, but the aliens are so paranoid that they are more determined to keep the superheroes away even while their ship is sinking into the magma. Meanwhile, the heroes rack their brains for a way to save the aliens before it's too late.

In The Simpsons episode "The Springfield Files", the trope is parodied when an alien (which later turns out to be Mr. Burns, made to look like an alien through various circumstances) greets the people of Springfield:

Inverted in one old Gumby short. Long story short, Pokey needed to be rescued from a group of Native Americans, so Gumby and some pilgrims storm their camp and send the natives running with gunfire. Immediately thereafter, they claim that they "come in peace."